Wilwood used to make a matching rear bracket for these calipers but the have long since stopped. I have them on a 9" on my Mustang. I also have a set on my VSE Cobra but the brackets were welded to the axle directly vs. the wilwood that had a combo for the Dynalite rear and puck type caliper. For the IRS I don't have much of a clue, but you could make a bracket that mounts both the Dynalite and the Puck Caliper likely pretty easily. What seems to be the easier route for parking brakes are Cobra Calipers (I think that is where they are off) that have the integral brake lever. And as long as you can get the brake pad of your desire might be a good way to go. Wilwood also has a new caliper with the mechanical ebrake, not sure if it is Dynalite style or more OEM'ish. The only down side might be getting brake pads in racing compounds, but I would expect that might not be such a problem these days.
Just found this with the cobra brake
http://www.fortesparts.com/catalogDisplay.cfm?cat=3